The invention relates to an air filter system, particularly for use as an air filter of an internal combustion engine, and a filter element for installation in such a filter system.
A filter system with a filter element for internal combustion engines is known from WO 2009/047196 A1. This filter system is particularly used for the filtration of the induction air of an internal combustion engine and consists of a housing and a cover for holding the filter element, wherein, by virtue of the design of the seals of the filter element with two toroidal configurations and a sealing groove in-between, a sealing effect, on the one hand, and, on the other hand, an axial support of the filter element in a housing are ensured. Especially when using synthetic material for the seal on elements that are subject to vibrations, a design is required that will also function reliably during extreme temperature fluctuations.
WO 2009/047196 A1 describes furthermore that a secondary element is provided, which is positioned in the interior of a filter element of the filter system. The purpose of the secondary element is keeping the outlet of the filter system closed during the filter element replacement, preventing any contamination from getting into this area while the filter element is being cleaned or replaced. During filter system operation, the purified air flows through the secondary element, which has a fleece layer on a supporting structure. The secondary element is attached to the outlet connection of the outlet by means of a screw thread and at the same time is sealed in this area by means of an O-ring.
In principle it is envisaged to replace the filter elements of air filters after a certain operating time. Depending on the amount of accumulated dust, the service life of an air filter can be only a few days (construction equipment) or up to several months. In this context, the secondary element that is arranged on the clean air side usually remains in the filter system. If the secondary element is also heavily contaminated, however, then it must also be replaced, since otherwise the airflow will be reduced excessively. For this purpose it is particularly important that the filter element and the secondary element are reliably sealed in a housing to ensure safe operation, in order to protect the induction tract of a downstream internal combustion engine against penetration of contamination.